1. Field of the Invention
The invention relates to a debarking shaft arrangement for a debarking machine, and more particularly to a debarking machine in which the debarking shafts are configured to permit reversible installation and use.
2. Description of the Related Art
Debarking machines for debarking logs typically employ a number of rotating debarking shafts provided with a number of teeth extending beyond the circumferential surface of the shaft. The teeth are adapted to strip bark off the logs transversely to the length of the logs and at the same to convey the trees transversely relative to the shafts. The shafts constitute at least a part of a support surface, upon which the logs travel through the debarking machine. Related debarking machines are described in U.S. Pat. Nos. 4,685,498 and 5,394,912.
A problem with the above type of prior known debarking machines is the inconvenience and high cost of repairing worn or damaged teeth. The teeth must be repaired one at a time while the debarking shaft remains stationary in the debarking machine.
To eliminate this drawback, a debarking machine in accordance with the present invention incorporates a debarking shaft system in which the debarking teeth associated with each shaft are designed to be effective in opposite rotating directions of the debarking shafts. Further, the debarking shafts are designed to be reversible. The inventive debarking machine enables a speedy deployment of new teeth just by removing and securing a shaft at 180xc2x0 relative to the original position (reversed), whereby it is parallel to the original position but has an opposite rotating direction with respect to the original position.
Debarking teeth in accordance with the present invention have two working faces arranged to be effective in opposite rotational directions of the shaft to which they are mounted. The teeth on each working face can be different from or similar to each other. When using dissimilar teeth in the opposite rotating directions of a shaft, a different debarking capacity will be obtained in various rotating directions, e.g. for wintertime barking and summertime barking. It is also possible to use sharp teeth first for the debarking of hard-to-bark or frozen trees, and to use worn teeth for the treatment of easy-to-bark trees.
In one preferred embodiment of the invention, the arrangement is such that the debarking shaft is designed and dimensioned such that a dislodged shaft, after being pivoted through 180xc2x0, is mountable in the same position or in a corresponding position. This arrangement is relevant primarily when the debarking machine is provided with two types of shafts that are compatible in terms of the mounting and symmetrical in terms of the axial pitch of teeth mounted thereto. In this preferred embodiment, every other shaft position is always provided with an identical shaft. The above expression xe2x80x9ca corresponding positionxe2x80x9d should be understood to indicate a shaft position compatible with the mounting and axial positioning of teeth mounted to the shaft as is further discussed below.
In particularly preferred embodiments of the invention, the arrangement is such that the debarking shaft is designed and dimensioned in such a way that a dislodged shaft, after being pivoted through 180xc2x0, is mountable in the position of an adjacent shaft or in a corresponding position. The expression xe2x80x9ca corresponding positionxe2x80x9d refers to those alternating positions for a debarking shaft in which the shafts lie co-directionally. This arrangement is applicable when all debarking shafts in a debarking machine are identical to each other. This arrangement offers the advantage that the debarking machine only requires a single type of spare shaft that is hence fit for all positions. In principle, such a shaft could be secured in the same position in each of its pivoted positions, but this would require e.g. different attachment points for different shaft pivoting directions.
In yet another preferred embodiment of the invention, attachment of a debarking shaft to a debarking machine is implemented in such a way that, in the process of dislodging, the shaft is liftable from its position and, respectively, in the process of installation, settable into its position from above the debarking mechanism.